The present invention relates generally to the presetting of ignition timing for internal combustion engines and more particularly to an ignition timing method and apparatus adaptable to a number of different ignition systems on a number of different engines requiring a minimum number of relatively economical components peculiar to the particular engine-ignition combination. Even more particularly the present invention relates to a keyed adaptor sleeve which allows the use of a standard flywheel on a variety of different engines, many of which may be provided with different optinal ignition systems requiring different ignition timing.
An internal combustion engine manufacturer typically offers a wide variety of engine designs and options. For example, both two stroke cycle and four stroke cycle engines may be offered, and engines of varying crankshaft sizes may be available. Numerous ignition options may be available with each of the engine designs including, for example, solid state capacitor discharge ignition arrangements as well as magneto or breaker point ignition or other conventional ignition configurations. Further, a given ignition arrangement may be obsoleted by an improved later developed ignition arrangement and each ignition arrangement may require different preset timing for optimum engine operation.
In copending application Ser. No. 923,997, assigned to the assignee of the present application, there is disclosed an ignition timing scheme for adapting the same flywheel and ignition configuration to, for example, either a solid state capacitor discharge ignition arrangement or a magneto ignition arrangement by the appropriate selection of a particular offset key joining the flywheel to the engine crankshaft with that key having an offset appropriate to the particular ignition system employed. While this arrangement eliminates the necessity for stockpiling two different flywheels as spare parts for the same engine design, different flywheels are required for different engine configurations, for example, for engines having different size crankshafts. Further, the physical location of the fixed part of the ignition system on the engine may vary widely from design to design while the timing variations available from the offset key arrangement in this prior application are limited to something less than the sum of the widths of the two keyways to be occupied by the offset key. It would be highly desirable to extend the ideas of the aforementioned copending application, the entire disclosure of which is specifically incorporated by reference herein, to a wider variety of engine designs.